Hydraulic feed control system



J1me H. F. VICKERS 2,285,069

HYDRAULIC FEED CONTROL SYSTEM Filed Sept. 29, 1957 2 Sheets-Sheet 1 INVENTOR. ///lP/ ?r 7 I/IC/(EPQ ATTORNEYS June 2, 1942. H. F. vlcKERs 2,235,069

' HYDRAULIC FEED CONTROL SYSTEM Filed Sept. 29, 1937 2 Sheets-Sheet 2 INVENTOR. HAPPI 7? l/m/(Ees ATTORNEYS Patented June 2, 1942 HYDRAULIC FEED CONTROL SYSTEM Harry F. Vickers, Detroit, Mich., asslgnor to Vickers, Incorporated, Detroit, Mich a corporation of Michigan Application September 29, 1937, Serial No. 166,298

2 Claims.

An object of the present invention is to provide a liquid pressure system utilizing a variable delivery pump, and a pressure compensating device therefor, a liquid pressure motor, a fourway or directional control valve, and an automatic reversing device for said motor. In systems using variable pumps it is a practice to set the pump corresponding to certain load and predetermined speed. Theoretically such a varible pump should maintain a constant speed of the liquid actuated element regardless of a varying load, but practically, there is a change in slippage in said pump which results in a slowing down when an increased load is met or an increase in speed equivalent to the amount of slippage when the load is released. In practice, with systems using a variable pump, fairly good results are often obtained when the work is first set up, but when the oil warms up and thins, and as the tools become dull, there is a noticeable slowing up due toa change in the slippage of the variable pump.

The present invention contemplates a flow control arrangement for a hydraulic system which will provide a constant speed of the hydraulicale ly actuated member regardless of the .load conditions and pump slippage. The system, in the main, consists of a combination of a variable delivery pump and a hydraulic speed control member disclosed in my British Patent, No..

399,609, dated June 11, 1932, together with an automatic pressure regulator and various control valves.

A further feature of the present invention is that the system will require a constant horsepower consumption. This allows the greatest efficiency in the performance of the power unit.

An illustration of the invention embodied in the hydraulic system having a reversible cylinder motor is set forth in the following description and accompanying drawings.

In the drawings: I

Fig. 1 shows the location of the various elements of the system in relation to a table drilling machine.

Fig. 2 is a partially diagrammatic view of the elements of the hydraulic system, said elements being shown in cross-section.

Referring to Fig. 2 the portion of a housing 4 is an enlarged portion of the liquid supply tank shown diagrammatically at la, in which is mounted a variable delivery pump Land a pressure compensating unit 8. -A motor I is arranged to drive the pump 5 which is hydraulically connected through a four-way valve 0 to a cylinder motor 9. A flow control valve l0 and a control valve H are also connected in the hydraulic circuit. I

Referring more specifically to the variable delivery pump, the pump part 5 is driven through a drive shaft I2 by the electric motor I or any other constant speed power means. The drive shaft l2 runs in ball or roller bearings within a bearing housing l3 and a. flange It, said flange being a part of the driveshaft. The drive shaft carries in a central bore a universal link I! which drives a cylinder block IS with the same angular velocity as the drive shaft. The cylinder block it bears upon a bearing pin l1 and a swivel yoke ll. The swivel yoke i8 is supported by means of a link I! which is connected to the pressure compensating unit 6. The cylinder block it is pivotally mounted on the bearing housing l3 by pins 20. A plurality of pistons 2| are mounted in axial bores or cylinders of the cylinder block it, said cylinders have axis of symmetry coincident with axis of the cylinder block. By means of piston rods 22 which are provided with universal spherical end bearings, the pistons 2| are in axial positive connection withthe drive shaft flange l4. g

I The variable delivery pumpis of the well known type wherein the volume of delivery of the pump is dependent on the angle between the axis of the drive shaft 12 and the axis of symmetry of the pistons 2|. For example, referring to Fig. 2 the pump would be in neutral position when the cylinder block it is in horizontal position, while the maximum volume positioned would be as shown with the swivel yoke l8 bearing against an adjustable stop 23. A flexible conduit 24 connects the inlet of the pump with the tank la and a conduit 24a, and a flexible conduit 25 connects the outlet of the pump to a conduit 26 which leads through the four-way valve 8, and conduit 26a which leads to the compensating unit 6.

The compensating unit 8 consistsof a small cylinder 21, one side of which is in communication with the main pressure line through the conduit 26a. A smaller cylinder or plunger 28 is slidably fitted co-axial with the bore of the cylinder 2'! and a spring 29 normally urges the cylinder 28 to its extreme position shown in Fig. 2. The flow control valve l0 which consists, in the main, of a balanced orifice valve 30 andan adjustable throttle 3| is adapted to maintain a predetermined differential pressure across the orifice of the throttle 3|. A control lever 22 is providedfor adjusting the throttle 3|. The fourway valve 8 is a standard type of four-way valve,

consisting of a housing 33 and a slidable Piston 34 operatively connected to an operating lever 35.

The cylinder 9 has one end directly connected to the four-way valve 8 by' a conduit 36 and has the other end connected to the valve 8 alternately through the flow control valve In and through the control valve II. A piston 31 is slidably mounted in the cylinder 9 and has a piston rod 38 bearing a drill member 39 and an adjustable cam block 40, said cam block being adapted to contact a slidable plunger 4| in the housing of the valve Ii.

In Fig. 1 the hydraulic feed control system is shown on a table drilling machine 42, where it controls cylinder motor 9 and the sliding head 44'.

In the operation: The variable delivery pump is driven through the coupling or universal link I5 by the motor 1. When the system is starting, the pressure in the compensating unit 6 is negligible and the spring 29 will serve to displace the pump housing against the stop 23. Oil under pressure will flow from the pump conduit 25 through conduit 26 to the four way valve 8 where it will be directed to the cylinder 9 through the conduit 36 when the valve piston 34 is in the position shown in Fig. 2. This pressure in the piston end of the cylinder will cause the piston 31 to move downwardly and will thereby force the oil in the rod end of the cylinder through a conduit 44, around a check valve 45, and through the control valve II and conduits 46 and 41 to.

the valve 8 where it will be directed to the tank conduit 24a.

This exhaust or tank oil will pass freely through the valve II causing rapid traverse of the piston until the cam 40 on the piston rod 38 depresses the plunger 4| thereby causing the closure of a port 48. The exhaust oilfrom the rod end of the cylinder will then be directed through a conduit 49 to the feed control valve II! where it will be metered at a constant rate through conduits 41 and 24a to the tank. The rate of movement of the piston 31 may be directly controlled by the adjusting of the throttle valve 3|.

The return of the piston 31 is accomplished by shifting the handle 35 of the four-way valve 8 'to move the valve piston 34 downwardly as shown in Fig. 2. In this position the four-way valve will direct pressure-from the pump to the conduits 41 and 46. Oil under pressure will pass around the plunger 4| and will open the check valve 45 to pass through conduit 44 to the rod end of the cylinder 9. The piston 31 will then be returned to starting position at rapid traverse rate. During this traverse the driving piston is locked between two columns of oil under pressure, thus insuring positive feed rates. The oil at the piston end of the cylinder 9 is forced through the four-way valve back to the tank. The rate of travel of the driving piston depends upon the relation of the piston rod area to the area of the cylinder.

It will be understood that during any given feeding stroke of the piston 31 that the flow controlling unit In maintains a fixed rate of exit of liquid from the bottom end of cylinder 9. Accordingly, there is also a constant rate of flow of liquid into the upper end of cylinder 9. It follows then that the compensating mechanism 6 will move the yoke I8 into a position where the pump displacement is equal to the rate of flow into the upper end of cylinder 9. The yoke I8 is positively maintained in such a position because if it tended to move toward neutral and thus decrease the rate or delivery into cylinder 9, the pressure would fall, thus permitting spr n 29 to overcome the force on piston 21 and move the yoke I8 upwardly. If the yoke I8 tended to move upwardly to a position or greater displacement than that corresponding to the rate of flow out of cylinder 9, the pressure would build up in lines 36 and 26, thus permitting piston 21. to overcome the force of spring 29 and bring the yoke back to its intended position.

The force of the spring 29 and area of piston 21, of course, are so chosen as to maintain in line 36 a pressure greater than that required to overcome the maximum resistance encountered at tool 39 plus the friction of movement of piston 31. Under conditions where the tool resistance is less than maximum, the additional resistance to movement of piston 31 is produced by building up pressure on the liquid in the bottom of cylinder 9 and in pipe 49. It is inherent that the pressure above piston 31 must be equal to the sum of the pressure below the same plus the tool resistance. Thus as the tool resistance decreases, the pressure in line 49 must increase so as to maintain this sum constant,

Since the action of the flow control device I0 is independent of the pressure in line 49, it is obvious that the piston 31 moves at a fixed rate. It is also obvious that since the stroke of the pump is automatically controlled to pump only the quantity of fluid required for driving the motor that no power is wasted in the device except the small quantity which escapes to the suction side of the system by the slippage in the pump itself. Of course, should a variation in slippage occur at the pump 5, the compensating mechanism 6 will automatically increase the stroke setting of yoke I8 slightly and sufliciently to make up for the additional slippage. The rate of flow from pipe 36 into cylinder 9, however, remains constant at any rate of slip in pump I8 because liquid canno flow into cylinder 9 faster than it can flow out of the same. If the tool 39 meets with any unusual resistance or if the operator fails to reverse the four-way valve when the piston 31 reaches its lowermost position, the pressure in the system will rise and the volume of the pump 5 will decrease. If the pressure reach es a maximum, the pump will deliver no liquid at all thus insuring no rupture of the system.

What I claim is:

1. In combination in a hydraulic system, a hydraulic motor having a piston and cylinder, a variable delivery pump for preloading the inlet side of the motor during the power stroke, said pump having a movable part for varying the delivery capacity, a spring pressed piston arranged to urge the movable part to on-stroke position, means connecting the pressure on the outlet side of the pump between the pump and the motor to said spring pressed piston to act in opposition to the spring whereby the volume output of said pump is proportional to the requirements of the system, and a speed control device including a chamber for receiving the liquid flow from the outlet side of the motor, a variable discharge orifice member, a chamber on the intake side of said orifice member, a valve between said two chambers, and a spring pressed piston operatively connected to said valve for controlling the pressure in said second named chamber to control the pressure differential and the flow across said orifice memher, one side of said pi ton being in direct communication with said second named chamber and the other side of said piston, which is the side upon which the spring acts, being in direct communication with the discharge outlet on the discharge side of the variable orifice member, said speed control device and said means cooperating to effect constant speed movement of said motor piston irrespective of pump slippage and resistance met thereby.

2. In a hydraulic power transmission system the combination of a variable displacement pump, a fluid motor, conduits forming a circuit extending from the pump outlet to the motor and from the motor to the pump inlet, means forming a predetermined restriction in said con- 15 duits, valve means responsive solely to the pressure differential across said restriction and connected to maintain such difierential substantially constant, and means responsive to slight variations in pump outlet pressure for controlling the pump displacement comprising a spring pressed piston arranged to put said pump on-stroke, and means connecting the pressure on the outlet side of the pump between the pump and the motor to said spring pressed piston to act in opposition to the spring, said means coacting together to maintain the motor speed substantially constant independently of variations in motor load and of variations in pump slippage.

HARRY F, VICKERS. 

